Forget the narcolepsy; forget the lip-lock controversy (on which reams have been written about). Naan Sigappu Manithan is first and foremost a tale of one man's quest for revenge. If Thiru's previous film, Samar, had the hero searching for the mysterious adversaries who were shaping his life, Naan Sigappu Manithan has the hero hunting for the unknown assailants who have raped and maimed his lover. As in Ghajini, whose formula this film faithfully follows to some extent, the film tries to camouflage the generic nature of its plot by giving its hero a fanciful medical condition; if it was short term memory loss in the former, here, it is narcolepsy.

Thiru actually builds a solid first half building on this sleep disorder, using it to fuel the film's humour, romance and interval twist. Like a guide, he takes us through the life of the narcoleptic Indran ( Vishal) and we see how the medical condition has influenced his life — at job interviews, he falls asleep on being told he has been selected; we learn he fainted after a classmate proposed to him in school; his incapability to have sex becomes a cause for amusement at a college demonstration; he always needs a 'driver' (Jagan slipping into the role of the hero's witty friend) to be taken to places; and, in a rare occasion when he decides to venture out alone, a blast of a vehicle's horn leaves him sleeping in the middle of the road, which also leads to him getting acquainted with Meera ( Lakshmi Menon, playing the angel to this 'flawed' hero). These scenes, in addition to Saranya Ponvannan's yet another naive mom act, contribute to the lighter moments in the film, and Thiru endears us to the characters that populate Indran's world.

While Ghajini's hero tattooed his body to aid his memory, Indran, here, writes down a list of things — from staying awake all day to kissing a girl and even watching a Shakeela film first day, first show — that he cannot (but yearns to) do. And, after Meera enters his life, he manages to strike out many of these items, and when we realize that he only has the last one — to fight for the right — remaining, we anticipate how this twist will arrive. And, it unfolds when mysterious men intercept their car atop an unfinished flyover. Indran panics and goes into sleep, while Meera, who is now pregnant with their child is gang raped. Now, she becomes the sleeper as she gets into a coma, and Indran decides to hunt down the assailants and avenge her. But, can he, with his medical condition?

There is intelligence in this script, like the hero's name which actually tells us about the one element that can neutralize his condition (which results in a cleverly done romantic scene with Meera and Indran) but Thiru slips quite a bit in the second half as he goes for one twist too many in explaining why Meera is attacked. So, we get a back story about one of Indran's friends involving adultery and blackmail, but the entire segment ends up being unintentionally funny because of the Wild Things-like manner in which characters change colours and the unconvincing performances of the miscast actors involved. Even the climax, despite featuring a couple of gory deaths, fails to fully capture Indran's rage towards the villains for maiming his lover, and what we are left with is a feeling of mild discontent, as a promising premise is compromised for a generic revenge drama.